1. Field of the Invention
This invention pertains to filament-forming melt-spinnable polyimide-esters and to high modulus filaments thereof.
2. Description of the Prior Art
A class of aromatic polyesters that form optically anisotropic melts from which oriented filaments can be melt-spun has been described in Schaefgen U.S. Pat. No. 4,118,372. These polyesters are derived primarily from para-oriented dihydric phenols and para-oriented aromatic dicarboxylic acids. Filaments that are melt-spun from such polyesters can be heat treated to high tenacity and modulus.
This invention provides a different class of anisotropic-melt-forming polymers which can be melt-spun into filaments of high as-spun modulus, i.e., greater than 177 dN/tex. The novel filaments can also be heat treated to increase tenacity while retaining moduli in excess of 177 dN/tex.
Polyimide-ester from 4-(4'-carboxyphthalimido) benzoic acid and ethylene glycol as disclosed in U.S. Pat. No. 3,377,321 is said to be useful for coatings and fibers. Polyimide-esters are also mentioned in U.S. Pat. No. 3,542,731. The chemical structures of the polymers of such patents are quite distinct from those of the present invention.